Browse Prior Art Database

Scan Linearity Correction Technique

IP.com Disclosure Number: IPCOM000049045D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Latta, MR: AUTHOR [+2]

Abstract

This article describes a method for scan linearity correction in a laser optical scanning system which includes the steps of accurately measuring the nonlinearity of a particular laser optical scanning system, producing a correction algorithm based on the measured data, and programming the algorithm into the data clocking software of the control unit of the apparatus.

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Scan Linearity Correction Technique

This article describes a method for scan linearity correction in a laser optical scanning system which includes the steps of accurately measuring the nonlinearity of a particular laser optical scanning system, producing a correction algorithm based on the measured data, and programming the algorithm into the data clocking software of the control unit of the apparatus.

It can be shown that the magnitude of deviation from linearity for a varying scan angle (see original) is proportional to tan (see original) and the velocity is proportional to sec 28. The table below shows, in the last column, the creases, the deviation from linearity progressively worsens.

The plot of the deviation from linearity for a specific holographic deflector system is shown in the graph. In this system, the half-field deflection encompasses 22 scan elements (1/2 degree per scan increment) to generate a seven-inch-wide scan. If the deflection is corrected at full field, the maximum deviation is about -33.9 mils at about 4.1 inches, as shown in the lower curve of the figure on the next page. If the system is refocused for minimum + excursions, the deviation can be reduced to + 22 mils, as shown in the upper curve.

Based upon the above data, our method would be to measure the actual scan position at one inch increments across the scan utilizing an appropriate test fixture, and fit a curve to the scan measurements obtained. The scan non- linearity is then co...